text: A pyrogallolarene (also calix[4]pyrogallolarene) is a macrocycle, or a cyclic oligomer, based on the condensation of pyrogallol (1,2,3-trihydroxybenzene) and an aldehyde. Pyrogallolarenes are a type of calixarene, and a subset of resorcinarenes that are substituted with a hydroxyl at the 2-position.
  Pyrogallolarenes, like all resorcinarenes, form inclusion complexes with other molecules forming a host–guest complex.  Pyrogallolarenes (like resorcinarenes) self-assemble into larger supramolecular structures forming a hydrogen-bonded hexamer. The pyrogallolarene hexamer is unique from those formed from resorcinarene, in that it does not incorporate solvent molecules into the structure. Both in the crystalline state and in organic solvents, six molecules will form an assembly with an internal volume of around one cubic nanometer (nanocapsules) and shapes similar to the Archimedean solids. A number of solvent or other molecules may reside in the capsule interior.  The pyrogallolarene hexamer is generally more stable than the resorcinarene hexamer, even in polar solvents.